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Calorifier safety valve drain

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martijnvdh View Drop Down
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    Posted: 28 July 2022 at 10:17
Coming back to this mountain of knowledge and experience for some more advice. 

Our 371 has a 20ltr Isotemp hot water calorifier installed under the bed in the aft port cabin. The calorifier has a 220V heating coil and is also connected to the engine cooling water. 

As is necessary, the calorifier is fitted with an overpressure safety valve. This spits out a little bit of water while the contents of the calorifier heats up (and expands). But…the water is just relased into the underlying locker which then overflows into the engine bay bilges. With regular use I’d say about 1 to 2 litres a week is released. Not a massive amount, but as this is now the only source “wetting” the bilges I would prefer to eliminate it. 

Had anybody been successful in rerouting this drainvalve to somewhere? An overboard connection maybe? As thisnis all happening in the bottom of the boat, a gravity feed to elsewhere is not going to work. 

For now I have placed an empty yoghurt tub under the valve and empty it every few days…
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JUTTER View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JUTTER Quote  Post ReplyReply Direct Link To This Post Posted: 28 July 2022 at 10:44
Hi,

In my H350 (2010) there is exactly the same calorifier in the same location. 

Here is my solution for water coming out of the overpressure valve. 

I have connected a thin plastic tube to the valve and , following some other ducts/cables, I have led it into the bilge under the sink in the heads. There the tube is led through a hole in the cap of a closed plastic bottle, easily accessible through the small door under the sink for emptying.  


Claude


JUTTER, Hanse 350#0256, 2010, deep keel, Zeeland
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350Bob View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 350Bob Quote  Post ReplyReply Direct Link To This Post Posted: 28 July 2022 at 11:13
We have a very similar system to Jutter, a clear PVC hose pushed over the outlet from the pressure relief valve, then up through the finger hole in the access hatch and into a small plastic bottle through the screw on lid. It is the first item on the daily engine checks to empty the bottle.

Not the most professional system but very effective.

Bob
H350 #205
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fendant Quote  Post ReplyReply Direct Link To This Post Posted: 28 July 2022 at 16:54
Same here, I am using a 5 ltr PE canister.
Normally I have only 1- 2 ltrs in it.
I am switching off the water pressure system, when we are not on the boat.
The 220 V supply to the water heater however stays on.
Frank
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S&J View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote S&J Quote  Post ReplyReply Direct Link To This Post Posted: 28 July 2022 at 18:31
I think this is poor design by Hanse.  
Mine seems to produce more overflow from the electric heater than the engine.
On the 458 there is a dedicated sea-cock that drained the recess for the cockpit hatch slides.  Thinking of diverting my small bore pipe to this to avoid having to empty the bottle.  Haven't found a suitable way to add the plastic tube to the wider drainage tube yet...
H458 #159 Primal Mediterranean cruising
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perry View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote perry Quote  Post ReplyReply Direct Link To This Post Posted: 28 July 2022 at 18:32
If you fit a pressure accumulator the expansion of the heated water will not excede the blow off pressure of the pressure relief valve.
Having said that the PRV fitted to my old Isotherm Calorifier was very low quality similar can be bought from China. I have sourced a better quality domestic PRV from local plumber shop, but you have to fit an additional one way valve [our plumbers call them "check Valves]. As the Iso therm PRV has an inbuilt one way valve.
I recently bought a replacement for the failed [corrosion]  Isotherm calorifier and an accumulator from UK company [Surejust]. same price as Isotherm, but made of quality materials with good valves.

Regards
Perry

Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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MasterKeil View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MasterKeil Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2022 at 09:01
1. When the water is heated electrically then the overpressure valve should not open. If it opens, then the thermostat is not adjusted correctly.
2. When the water is heated by the engine, then the thermostat is bypassed. To prevent overheating and the overpressure to open we alway switch off the pressure pump and open the hot water tap. Then there is some water coming out of the tap, after a few minutes it stops. Then the water has expanded enough.
Hanse 370#640 "Nemesis"
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perry View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote perry Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2022 at 10:37
The thermal expansion coefficient for water is approx 210 ppm/deg C
To heat your calorifier by electric or engine to same temperature will have same expansion.
water heated from 20-60 deg C will expand 40* 210 e-6 *20000 ccm = approx 170ccm
Ignoring the expansion of the tank volume  approx <1ccm

In some yachts the numerous rubber hoses in the hot water system will accomodate this amount of expansion. Some calorifiers are plain steel [NOT:- Copper, stainless, acier inox, rostfreier Stahl] pressure vessels with vitreous enamel liner. heat and pressure cycling may limit their life as the vitreous enamel coat detaches.

Yes,  one solution is to turn pump off, open tap to de-pressurise system every time you heat the calorifier.
We forget this  and so have fitted the pressure accumulator vessel which also benefits by reducing the pump cycles.
Bottom line is a good system should be built to work with thermal expansion of water, not just vent off to protect the pressure vessel.
Regards
Perry


Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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martijnvdh View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote martijnvdh Quote  Post ReplyReply Direct Link To This Post Posted: 30 July 2022 at 20:53
Hi Perry,
What size accumulator did you fit?
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perry View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote perry Quote  Post ReplyReply Direct Link To This Post Posted: 30 July 2022 at 21:05
2 lires seems fine. On Bloto today, and my wife says the pump runs less and doesnt sound as harsh. Result!   The treasurer is Happy!
Perry
PS I see your in Belgium, My mother in law was borm Antwerp [Folkstraat], still got familt there.


Edited by perry - 30 July 2022 at 21:06
Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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